1. Field of the Invention
The present invention relates to a gas discharge panel in which electric discharges are generated across electrodes in an enclosed gas, such as a plasma display panel, and an evacuation method therefor. More particularly, the invention relates to a structure of a gas discharge panel which facilitates gas evacuation and gas introduction in the fabrication of the panel and to an evacuation method therefor.
2. Description of the Prior Art
Gas discharge panels are self-luminous panels which have an electric discharge space defined between a pair of substrates spaced a minute distance in an opposed relation with the periphery thereof being sealed with a sealing member of a sealer, and are applied to plasma display panels (PDPs) for wall-mount TVs.
PDPs capable of color display typically have a display area defined within an electric discharge space partitioned by barrier ribs. In a matrix-addressable Ac-driven PDP of the triode surface discharge type, for example, a plurality of elongate barrier ribs each having a height of about 100 .mu.m to about 200 .mu.m and a width of about 30 .mu.m to about 50 .mu.m are arranged parallel to each other at an interval of about 200 .mu.m in a striped configuration within the display area. A non-display area having a width of about 1 cm to about 3 cm, for example, is provided adjacent to a sealing member to surround the display area in which the barrier ribs are formed, for prevention of contamination by gases emanating from the sealing member.
The electric discharge space partitioned by the barrier ribs is filled with a discharge gas such as Xe or Ne.
The introduction of the discharge gas is typically achieved in the following manner. As shown in FIG. 33, a rear substrate 52 formed with barrier ribs 51 has a vent hole 54 formed in a corner thereof within an area to be surrounded by a sealing member 53. As shown in FIG. 34A, a sealer 56 of a low melting point glass is applied on a peripheral portion of a front substrate 55 for formation of the sealing member 53, and then the front substrate 55 and the rear substrate 52 are combined together with the sealer 56 melted by application of heat. In this heating process, a glass vent pipe 57 is attached to the vent hole 54 formed in the rear substrate 52 by using the low melting point glass as an adhesive.
Thereafter, impurity gases are expelled from the resulting panel through the attached vent pipe 57 as shown in FIG. 34B. Then, the discharge gas is introduced into an electric discharge space of the panel from the same vent pipe 57 as shown in FIG. 34C and, when the internal pressure of the panel reaches a desired level, the opening of the distal end of the vent pipe 57 is sealed. Thus, a PDP is completed.
In the case of the PDP having the barrier ribs arranged in a striped configuration in the electric discharge space, however, the barrier ribs obstruct gas flow in the electric discharge space during the evacuation and the gas introduction. More specifically, since the gas flow conductance (easiness of gas flow) of an inter-rib space (elongate cavity) defined between each adjacent pair of ribs is lower than the gas flow conductance of a peripheral space defined between the sealing member 53 and a barrier rib formation area, the impurity gases to be expelled from the panel flow through the peripheral space as indicated by arrows S in FIG. 35 when the panel is evacuated. Similarly, the discharge gas introduced into the electric discharge space flows through the peripheral space as indicated by arrows T in FIG. 36.
The impurity gases and the discharge gas mainly flow through the peripheral space in the PDP, and only a little portion thereof flows through the inter-rib spaces. Therefore, the impurity gases emanating from the barrier ribs, the sealing member and the like due to the heat applied during the panel sealing process cannot sufficiently be expelled from the inter-rib spaces, so that the impurity gases remain in the inter-rib spaces and are re-adsorbed on the interior surface of the panel. In the case of the AC-driven PDP, the impurity gases contaminate a protection film of MgO, thereby deteriorating the display characteristics of the PDP. This problem may be solved by performing the impurity gas expelling operation for a prolonged time, but the time required for the panel fabrication is increased, resulting in a lower productivity.
In the case of the PDP having the stripe barrier ribs, the nonuniform gas flow conductance attributable to the internal structure of the PDP makes it impossible to completely remove the impurity gases from the PDP in a short time by an evacuation method utilizing a pressure difference.
As a method for forcibly removing the impurity gases remaining in the inter-rib spaces, a method is proposed in which the impurity gases are expelled by way of gas exchange by introducing a cleaning gas into the panel while heating the panel (see Japanese Unexamined Patent Publication No. Hei 5(1993)-234512).
More specifically, two vent holes are formed in a diagonally opposite relation in the rear substrate of the panel. The impurity gases are expelled from one of the vent holes and the cleaning gas is introduced from the other vent hole while the panel is heated.
However, this method also fails to completely remove the impurity gases remaining in the inter-rib spaces because the impurity gases and the cleaning gas flow through the peripheral space rather than through the inter-rib spaces as indicated by arrows U in FIG. 37. Hence, there is a demand for a technique by which the impurity gases can completely be removed from the PDP having the stripe barrier ribs.